Telephone set circuit



Get. 26, 1943. H. M. BAS COM 2,332,551

TELEPHONE SET CIRCUIT Filed June 22, 1942 /Nl/ENTOR H. M. BA 5 C 0M far 4,

A TTO NE) Patented Oct. 26, 1943 1 UNITED STATES PATENT o FicJE TELEPHONE SET CIRCUIT lienry M. Bascom, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y, a corporation of New York Application June 22, 1942, Serial No. 441,974 (01. 179-81) f 14 Claims.

This invention relates to telephone set circuits.

An' object of this invention is to enable signaling from the circuit of a portable telephone set without the use of a hand-operated generator.

Another object of the invention is to' enable the means for signaling out of a telephone set to be employed also as a portion of the receiving circuit of the set.

A further object of the invention is so to include amplifying means in the circuit of a telephone set that the amplifying means may be used alternatively for amplifying speech currents incoming to the set and for generating signaling currents for signaling out of the set.

' In accordance-with the invention, a telephone set circuit may embody amplifying means that, by operation of suitable switching means, may be included in the receiving circuit of the set circuit in order to amplify speech currents incoming thereto; and, alternatively, that, by operation of suitable switching means, may be included in an oscillating circuit for thegeneration of a signaling current for signaling out of the setcircuit. The amplifying means may be a so-called mechanical amplifier, that is, one that includes a receiver element and a microphone element; The oscillating circuit including the amplifying means may be so arranged that the sustained oscillation is illustrative of a telephone set circuit embody:

ing the invention.

With reference to the drawing, the circuit configuration and the character ofthe components of the circuit of a telephone set in accordance with this invention are shown. The telephone set comprises a pair of line terminals I0, '20, an incoming signal device or ringer 30, a condenser 40' for connection in series with the ringer, a multiwinding induction coilor transformer 50, a telephone receiver 60, a telephone transmitter 10, a condenser 80' forinclusion in the speech currents circuit of the set, a source of current or local battery 90, a normally open pair of contact-springs or contacts I00, a key operated switching means or device H0, an amplifying device or means I20, a source of current or second local battery I30, a second multiwinding transformer or induction coil I40, and a resistor I50.

All of these components may be'housed or sup ported within or on a single container or unit. The receiver and the transmitter may be included in a handset,"or ina chest transmitter and headelement I22 having a common diaphragm I23.

The mechanical amplifier may be such as is shown in A. F. Bennett et a1. Patent 2,242,284, of May 20, 1941, for Mechanical amplifier. 5 The switching device Hi] may comprise a manually operable two-position key or button III, a contact spring pile-up or assembly S and a second contact spring pile-up or assembly A. Ihe key.

I I I is shown in its neutral or mid-position under which condition'contact pairs I, 3 and E of assembly S are open,and contact pair 2 of assembly S is closed, and contact pairs I, 2 and 4 of assembly A are open and contact pair 3 of assembly A is closed. When the key II 1 is operated to the S position, that is, to the left, contact pairs I, 3 and 4 of assembly S are closed, and contact pair 2 of assembly S is open. When the key i Ii is moved or adjusted to its A position, that is, to the right, contact pairs I, 2 and i of assembly A are closed, and contact pair 3 of assembly A is opened. The contact switch I00 may be of the 'socalled push-to-talk type, that is, j pressure applied; for example, by the fingers of the user of the set, is required to maintainthe switch closed. Provision of a push-to-talk switch insures that when the set is not in use there is no drain on the local battery 90, and that, when the set is in use,

the user when not talking may economize with respect to the local battery 90 as Well as minimize noise pick-up by the transmitter. It will be observed that, when the key or button HI of the switching device H0 is in its mid or neutral position, there is no drain on the second local bat-- tery I30, the obvious circuits for that battery be ing open at contact pairs 3 and 4 of assembly S and at contact pairs I, 2 and 4 of assembly A.

The multiwinding transformer 56 comprises three windings 5|, 52, 5 3, serially connected with the condenser and contactpair 2 of switch assembly S across the line terminals I0, 20. The transmitter 10, contact pair I00 and-the local bat tery 90 constitute a series-connected circuit across winding 52 of the induction coil. The receiver 60 and contact pair 3 of switch assembly A are serially connected across the series-connected transformer winding 53 and condenser 80. The windings of transformer 50 are wound on a common core and together with the receiver and transmitter constitute an anti-side tone circuit of the type shown in schematic in Fig. 1 of K. S. Johnson, Patent 1,396,760, of'November 15, 1921, for Signaling circuit. The winding 53 is proportioned so as to include sufficient resistance to constitute the balancing resistance or network in shunt with the receiver.

When signaling current is incoming to the telephone set circuit at the terminals I0, 20 thereof, supplied, for example, over a suitable line, for example, the standard stranded steel wire tele phone pair such as is used in military field telephone systems, and from an exchange or switchboard, for example, at the field headquarters point, the ringer 30 is actuated over apath from line terminal I0, ringer 30, condenser 40, contact pair 2 of switch assembly S to terminal 20.

With the receiver 80 at his ear and the transmitter I adjacent his mouth, the called party, after closing the push-to-talk switch I00, may respond and transmit speech currents out of the set circuit through the line terminals I0, 20, and receive speech currents incoming over the telephone line through the terminals I0, 20.

If the attenuation overthe telephone line or pair is severe, or if the noises or other disturbances in the vicinity of the set circuit are unduly great, the speech currents incoming to the set circuit may be amplified in the receiver 60 by adjusting the key or button III of the switching device III) to its A position. Contact pairs I, 2 and 4 of switch assembly A are closed and contact pair 3 of switch assembly A is opened as a 1 result of this adjustment, and the amplifying means I is connected in the receiving circuit of the set. The opening of contact pair 3 of assembly A opens the normal circuit for the receiver 60, and the closure of contact pairs I and t of assembly A closes a local circuit for the receiver 60 that comprises receiver 60, contact pair 4 of assembly A, microphone element I2I of the amplifying means, local battery I30, contact pair i of assembly A back to the receiver 60. Closure of contact pairs 2 and 4 of assembly A substitutes the receiver element I22 of the amplifying means for the receiver 66 over the following circuit: Common terminal of windings 52 and 53 of transformer 59, wire I, contact pair 4, receiver element I22, wires 2, 3, contact pair 2, wire 4, to the line terminal side of condenser 80. For this adjustment of the switching device I I0, incoming speech currents do not directly traverse receiver 60 but flow through the receiver element of the amplifying means. Since the receiver element is coupled to the microphone element of the amplifying means, and the receiver til is connected in series circuit with the microphone element and battery I30, the variation in the resistance of the microphone element in response to the speech current flow in the receiver element produce amplified variations of the current flow in such local circuit, whereby the effects of severe attenuation in the telephone line or of the noise or other disturbing. conditions at the telephone set, are overcome or minimized. When the set circuit is not in use, the key or button III should be restored to its neutral or mid-position, thereby restoring assembly A to the condition shown on the drawing, whereby the local amplifying circuit for the receiver 80 is opened, relieving the battery I of any strain thereon.

The procedure to be observed when it is desired to signal out of the set is as follows: The key or button III of the switching device H0 is adjusted or moved to its S position, whereby contact pairs I, 3 and 4 of switching assembly S are closed and contact pair 2 of assembly S is open. The opening of the latter-mentioned contact pair 2 disconnects the transmitting, receiving and incoming signaling circuit from across the line terminals. Closure of contact pair I of assembly S connects the secondary winding I II of transformer I across the line terminals. Closure of contact pairs 3, 4 of assembly S completes a local circuit for the microphone element of the amplifying means and a local circuit for the receiver element of the amplifying means. The local circuit for the microphone element may be traced from terminal I24, battery I30, primary winding I42 of transformer M0, resistance I50, contact pair 3 of assembly S, terminal I25, microphone element I2I to terminal I24. The local circuit for the receiver element may be traced from terminal I25, receiver element I22, terminal I26, contact pair 4 of assembly S, resistance I50, contact pair 3 of assembly S, backto terminal I25. It is apparent that the resistance E is common to the two local circuits for the amplifying means. This resistance constitutes a feedback element for coupling the two local circuits, whereby energy in the 10- cal circuit of the microphone element is fed back to the local circuit of the receiver element to be further amplified in the microphone element circuit. This regenerative process, by appropriate proportioning of the resistance I50, may be allowed to proceed to the sustained oscillation point which, with a voice frequency mechanical amplifier of the aforesaid Bennett et a1. Patent 2,242,284, may provide an electric Wave of a frequency of the order of 1000 cycles per second. The electric wave generated in the microphone element local circuit is induced in the secondary winding of the transformer I 30 and applied through the terminals I0, 20 to the telephone line connected to the latter. At the central oiflce or switchboard, the signaling current transmitted thereto from the telephone set circuit may be employed to actuate a relay to energize a line lamp or to operate a signal drop.

Although this invention has been disclosed with reference to what is believed at this time to be a preferred embodiment thereof, it will be understood that it is not limited thereto but is capable of other exemplifications without departing from the spirit or scope of the inventive concept disclosed.

What is clamed is:

1. A telephone set circuit including means for generating signaling current to be transmitted out of said circuit, said means comprising an amplifier, a normally-open feedback connection for said amplifier, and means to close said connection for regenerative feedback therethrough wherebysaid amplifier generates sustained current for transmission out of said set circuit.

2. A telephone set circuit including line ter minals, an incoming-signal circuit, a speech current receiving and transmitting circuit, said sig nal and speech circuits being normally connected across said terminals, and means for signaling out of the set circuit through said line terminals,

said means comprising an amplifier, a normallycpen feedback connection for said amplifier, and means simultaneously to disconnect said incoming-signal circuit and said speech circuit from said line terminals, to connect said signalingout means to said line terminals, and to close said feedback connection for regenerative feedback through the latter.

3. A telephone set circuit comprising means for signaling out of said circuit, said means including a mechanically interconnected microphone element and receiver element, a multiple Winding transformer, a resistor, a normally-open series circuit comprising said microphone element, a source of current, one transformer winding and said resistor, a normally-open series circuit for said receiver element comprising said receiver element and said resistor, and means to close said normally-open circuits whereby said normally-open circuits are regeneratively interconnected through said resistor.

4;. A telephone set circuit comprising a receiving circuit including a receiver, an amplifier, and means for connecting said amplifier in circuit with said receiver to amplify speech currents incoming to said receiving circuit and alternatively for connecting said amplifier so as to oscillate for signaling out of said set circuit.

5. A telephone set circuit comprising a speech current receiving circuit including a receiver, an amplifier, means for connecting said amplifier in circuit with said receiver to amplify speech currents incoming to said receiving circuit, and means for interconnecting the output and the input of said amplifier for regenerative feedback such that the amplifier is caused to generate oscillations for signaling out of said set circuit.

6. A telephone set circuit comprising a speech current receiving circuit including a receiver, an amplifier of the type including a microphone element and a receiver element, means for connecting said amplifier in said receiving circuit to amplify speech currents incoming to said receiving circuit, and means to interconnect said microphone and rec'eiver'elements so that the amplifier generates oscillations for signaling out of the set circuit.

'7. A subscribers station comprising a receiving circuit including a receiver, a transmitting circuit including a transmitter, means for signaling out of said set circuit, and line terminals to which said circuits are connected; said means comprises a mechanically-interconnected mi crophone element and receiver element, a multiple winding transformer, a. resistor, a normallyopen series circuit comprising said microphone element, a source of current, one transformer winding and said resistor, a normally-open series circuit for said receiver element comprising said receiver element and said resistor, and means to close said normally-open circuits whereby said normally-open circuits are regeneratively interconnected through said resistor, the oscillatory current in the transformer winding being transmitted out of the station through a second transformer winding and said line terminals.

8. A telephone set circuit comprising a'speech current receiving set including a receiver, an amplifier of the type including a microphone element and a receiver element, means for substituting the amplifier-receiver element in said receiving circuit for said receiver and for connecting said amplifier-microphone element in a series circuit with said receiver to amplify speech current incoming to the receiving circuit, and

means for interconnecting said microphone and receiver element so that the amplifier generates oscillations for signaling out of the set circuit.

9. A telephone set circuit including means for generating signaling current for transmission out of said circuit, said means comprising an amplifier of the type including a microphone element and a receiver element, a normally-open feedback connection for interconnecting said microphone element and said receiver element. and means to close said connection for regenerative feedback therethrough.

10. A telephone set circuit including means for generating signaling current for transmission out of said circuit, comprising an amplifier of the type including a microphone element and a receiver element, a normally-open local circuit for said microphone element including an impedance, a normally-open local circuit for said receiver element including said impedance, and means to close said normally-open circuits whereby said local circuits are regeneratively interconnected through said impedance.

11. A telephone set circuit including means for generating signaling current for transmission out of said circuit, said means'comprising an amplifier including a microphone element and a receiver element, a normally-open local circuit for said microphone element including a resistance, a normally-open local circuit for said receiver element including said resistance, and means for closing said normally-open local circuits whereby said local circuits are regeneratively interconnected through said resistance.

12. A telephone set circuit including line terminals, an incoming signal circuit, a speech current receiving and transmitting circuit, said signal and speech circuit. being normally connected across said terminals and said speech circuit including a receiver, an amplifier coinprising a microphone element and a receiver ele- -ment, a normally-open feedback connection between said microphone and receiver elements, means for simultaneously substituting the amplifier-receiver element for said receiver in the speech circuit and for connecting said receiver and the amplifier-microphone element in a local series circuit, and means for simultaneously disconnecting said incoming signal circuit and said speech circuit from said line terminals, closing 14. The circuit of claim 13 in which said converting means simultaneously disconnects the speech circuit from the line terminals, establishes an oscillatory regenerative connection within the amplifier, and connects the converted amplifier to the line terminals.

' HENRY M. BASCOM. 

